Em Fri, Oct 11, 2019 at 05:19:42PM +0800, Leo Yan escreveu:
> When execute task exit testing case, Perf tool stucks in this case and
> doesn't return back on Arm64 Juno board.
>
> After dig into this issue, since Juno board has Arm's big.LITTLE CPUs,
> thus the PMUs are not compatible between the big CPUs and little CPUs.
> This leads to PMU event cannot be enabled properly when the traced task
> is migrated from one variant's CPU to another variant. Finally, the
> test case runs into infinite loop for cannot read out any event data
> after return from polling.
>
> Eventually, we need to work out formal solution to allow PMU events can
> be freely migrated from one CPU variant to another, but this is a
> difficult task and a different topic. This patch tries to fix the Perf
> test case to avoid infinite loop, when the testing detects 1000 times
> retrying for reading empty events, it will directly bail out and return
> failure. This allows the Perf tool can continue its other test cases.
Thanks, applied.
- Arnaldo
> Signed-off-by: Leo Yan <leo....@linaro.org>
> ---
> tools/perf/tests/task-exit.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/tools/perf/tests/task-exit.c b/tools/perf/tests/task-exit.c
> index ca0a6ca43b13..d85c9f608564 100644
> --- a/tools/perf/tests/task-exit.c
> +++ b/tools/perf/tests/task-exit.c
> @@ -53,6 +53,7 @@ int test__task_exit(struct test *test __maybe_unused, int
> subtest __maybe_unused
> struct perf_cpu_map *cpus;
> struct perf_thread_map *threads;
> struct mmap *md;
> + int retry_count = 0;
>
> signal(SIGCHLD, sig_handler);
>
> @@ -132,6 +133,13 @@ int test__task_exit(struct test *test __maybe_unused,
> int subtest __maybe_unused
> out_init:
> if (!exited || !nr_exit) {
> evlist__poll(evlist, -1);
> +
> + if (retry_count++ > 1000) {
> + pr_debug("Failed after retrying 1000 times\n");
> + err = -1;
> + goto out_free_maps;
> + }
> +
> goto retry;
> }
>
> --
> 2.17.1
--
- Arnaldo
